1. Field of the Invention
The present invention relates to a data architecture of map data used in a mobile processor, such as a car navigation system, a mobile phone, a personal digital assistance or the like, or fixed computer terminals. The present invention also relates to a data architecture of update instruction data, a map data processing apparatus, and a map data providing apparatus that are adapted to updating the map data having the invented map data.
2. Description of the Related Art
A car navigation system conducts route planning (route seeking) from a place of departure to a destination, and presents an optimal candidate route resulting from route planning on a display device together with a road map. Similar functions can be achieved by other mobile processors, such as mobile phones and personal digital assistances, or fixed computer terminals.
A data architecture of map data used in an apparatus that can make route planning includes a data set for displaying road maps and another data set for route planning in order to enhance the speed of processing. For example, JP-8-292716-A discloses this kind of data architecture. According to JP-8-292716-A, data for displaying road maps comprise a group of link information units, each of which indicates a road and includes node information units indicating nodes (start points, endpoints and/or intersections) of the road. Data for route planning comprises a set of node data, wherein each node data part includes a node information unit indicating a node and adjacent-node information units indicating one or more adjacent nodes. Interconnection of roads can be recognized by tracking adjacent-node information units, route planning from a place of departure to a destination can be achieved on the basis of adjacent-node information units within the data for route planning. Consequently, necessary link information units indicating the candidate route can be acquired on the basis of the node information units corresponding to a candidate route resulting from route planning, and the optimal candidate route may be displayed.
In accordance with the above-mentioned conventional data architecture of map data, when data have been updated due to new construction or elimination of a road, replenishment of map data, and so on, it is contemplated that both of the updated data set for displaying road maps and the updated data set for route planning should be stored in each user's apparatus in order to accommodate the data set for displaying road maps and the data set for route planning to each other. The method for updating the data sets in each user's apparatus may include distributing storage media storing the updated data and distributing the updated data by communications. In any event, however, there is likelihood that only one data set is updated in a user's apparatus, whereby data mismatching may occur. Although storage media are distributed, update of one data set may fail for the reason of malfunction of the user apparatus. When data sets are distributed by communications, even the data set for route planning can be updated successfully, the update instruction concerning the data set for displaying road maps may not be received by an obstruction to communication. If a user apparatus thus stores data sets of different versions in a user apparatus, there is likelihood that although the apparatus can conduct route planning, it cannot show the optimal route on the display device.